As semiconductor devices are miniaturized, a contact portion of a transistor is miniaturized and, also, a gate structure is shifted from a planar type to a multi-gate fin structure that is a three-dimensional structure. In the contact portion, a Ti (titanium) film is formed on a Si (silicon) layer or a SiGe (silicon germanium) layer as a base, and silicide is formed by reaction between Si and Ti. As for a method for forming a Ti film, there has been developed a method for forming a contact portion by using CVD (Chemical Vapor Deposition) that ensures a better step coverage compared to sputter film formation.
The Ti film formation using CVD is performed by loading a substrate into a processing chamber and converting a gaseous mixture of TiCl4 (titanium tetrachloride) gas and H2 (hydrogen) gas into a plasma. At this time, Cl (chlorine) contained in TiCl4 are taken as an impurity into the Ti film and remains as an impurity in the Ti film formed on the substrate. Since the Ti film containing high concentration of Cl is unstable, the Ti film deposited in the processing chamber is peeled off and particles are generated. After the Ti film formation, TixClx or Clx remains in a vacuum atmosphere in the processing chamber. Thus, the surface of the Ti film formed on the substrate is etched and becomes rough. Accordingly, TixClx is adhered onto a backside of the substrate, which results in contamination of the substrate.
Therefore, after the film is formed on the substrate, post treatment is performed to stabilize the film by reducing and removing Cl in the Ti film by supplying NH3 (ammonia) gas into the processing chamber in which the substrate is provided and forming a TiN (titanium nitride) film by nitriding a surface of the Ti film.
When substrates are exchanged, the film is stabilized by removing Cl remaining in an atmosphere in the processing chamber in which no substrate is provided by using a plasma of the above-described gaseous mixture and forming a TiN film on the surface of the Ti film covering the inner surfaces of the processing chamber.
Between a process of cleaning an inside of the processing chamber and a process of forming a film on the substrate, pre-coating for forming a thin film in advance on an inner wall of the processing chamber, a surface of a mounting table, and a surface of a gas shower head for supplying a processing gas is performed. In a conventional case, the pre-coating film is stabilized by nitriding the surface of the Ti film by supplying NH3 gas into the processing chamber or generating an NH3 plasma.
However, as the Ti film becomes thinner due to the miniaturization of devices, the surface of the Ti film is nitrided by N (nitrogen) taken into the Ti film by supplying NH3 gas into the processing chamber in which the substrate is provided, and silicidation in an interface between the Ti film and the Si film is disturbed. Further, the pre-coating film is a TiN film, and the Ti film that has been formed on the inner wall of the processing chamber or on the surface of the gas shower head during the film formation on the substrate is nitrided to a TiN film during the exchange of substrates. Therefore, the TiN film is sputtered by a plasma generated during the film formation on the substrate, specifically by Ar+ ions, and N is taken into the film formed on the substrate, which also disturbs the silicidation. As a result, if the miniaturization of devices progresses further, it is difficult to form a contact having a low resistance.
Japanese Patent Application Publication No. 2004-83983 discloses a technique for cleaning by introducing chlorine gas into a chamber in which a Ti film formation by plasma CVD is performed and decomposing a nickel chloride generated due to reaction between the chlorine gas and a nickel member in the chamber by hydrogen active spices. However, the components disclosed in the above-cited reference are different from those of the present disclosure.
Japanese Patent Application Publication No. 2004-232080 discloses a technique for intermittently supplying TiCl4 gas in a state where H2 gas is supplied into a chamber in which a Ti film formation by plasma CVD is performed. This technique has a purpose of realizing a low-temperature process while removing Cl in the film, which is different from the purpose of the present disclosure, and the method thereof is also different from that of the present disclosure.